Neurotmesis

• First step of peripheral nerve regeneration

  Schwaan cells de-differentiate and express a factor that attracts macrophages 
• Step after: Schwaan cells de-differentiate and express a factor that attracts macrophages 

  Macrophages fill the area between stumps and migrate to the DRG 
• Step after: Macrophages fill the area between stumps and migrate to the DRG 

  In the DRG macrophages express inflammatory factors that increase the expression of RAGs 
• Step after: In the DRG macrophages express inflammatory factors that increase the expression of RAGs 

  Macrophages in distal stumps clear away debris 
• Step after: Macrophages in distal stumps clear away debris 

  Macrophages in the stump express VEGF to increase proliferation and migration of endothelial cells 
• Step after: Macrophages in the stump express VEGF to increase proliferation and migration of endothelial cells 

  Endothelial cells make new vascularization that crosses the area without nerve 
• Step after: Endothelial cells make new vascularization that crosses the area without nerve 

  Schwaan cell precursors migrate across the endothelial cells to form Bands of Bungner 
• Step after: Schwaan cell precursors migrate across the endothelial cells to form Bands of Bungner 

  Proximal stumps forms collaterals, some of which may migrate to reach target 
• Step after: Proximal stumps forms collaterals, some of which may migrate to reach target 

  Bands of Bungner express NGF to keep nerve cells alive while they grow back the target